1. Field of the Invention
The invention relates to prior art suspended ceilings that use beams roll-formed of sheet metal in a grid that supports relatively light weight loads, such as panels. The beams have an inverted T-cross section with a vertical web, horizontal flanges extending opposite from one-another at the bottom of the web, and a bulb at the top, and optionally along, the web. Such beams are interconnected into a grid having rectangular openings that support panels on the flanges of the beams. The grid is supported from an overhead structure by hang wires. In some instances, the grid supports other light loads, such as signs, or other visual decorative elements.
2. Description of Related Art
Relatively light roll-formed sheet metal beams of the type described above and used in the present invention are shown, for instance, in U.S. Pat. Nos. 5,979,055 and 6,138,416. Such light beams are arranged into a grid, as shown, for instance, in U.S. Pat. No. 6,763,642.
Such suspended ceilings, with such relatively light sheet steel roll-formed metal grid beams that support panels, provide a pleasing cover over a room, with a minimum use of metal in the grid beams, since such a suspended ceiling structurally is designed to support only itself.
In some instances, however, light weight loads, for instance light fixtures, are hung below a suspended ceiling from the suspended ceiling grid by a clip on the ceiling grid, as shown for instance, in U.S. Pat. No. 3,612,461. In U.S. Pat. No. 4,073,458, there is shown a hanger clip for displaying light weight articles, such as sale signs, from a suspended ceiling. However, where it is necessary to support relatively heavy loads, such as data banks, below a suspended ceiling, heavy forged metal beams are used in the prior art in the ceiling grid of the suspended ceiling, instead of the light roll-formed sheet metal beams described above. The prior art forged steel beams have threads in channels in the beams, that receive threaded rods, as seen for instance in U.S. Patent Publication 2012/0240495A1 published Sep. 27, 2012.